The proposed research will investigate hypothalamic mechanisms controlling the release of prolactin (PRL), growth hormone (GH), and luteinizing hormone (LH) from the adenohypophysis. The hypothalamus will be anatomically mapped for sites at which applied electrical current will either increase or decrease the release of one of these pituitary hormones in both anesthetized and conscious sheep. Blood levels of hypothalamic hypophysiotropic hormones will be measured and correlated with both spontaneous and electrically induced changes in pituitary hormone release. By this means, we hope to determine for each pituitary hormone the relative roles of its releasing factor and its inhibiting factor in the physiological regulation of PRL, GH and LH release.